22. Regulation of the sacred liturgy depends solely on the authority of the Church, that is, on the Apostolic See and, as laws may determine, on the bishop.
[...]
Therefore no other person, even if he be a priest, may add, remove, or change anything in the liturgy on his own authority.

23. [...] Finally, there must be no innovations unless the good of the Church genuinely and certainly requires them; and care must be taken that any new forms adopted should in some way grow organically from forms already existing.
As far as possible, notable differences between the rites used in adjacent regions must be carefully avoided.

29. Servers, lectors commentators, and members of the choir also exercise a genuine liturgical function. They ought, therefore, to discharge their office with the sincere piety and decorum demanded by so exalted a ministry and rightly expected of them by God's people. Consequently they must all be deeply imbued with the spirit of the liturgy, each in his own measure, and they must be trained to perform their functions in a correct and orderly manner.

30. To promote active participation, the people should be encouraged to take part by means of acclamations, responses, psalmody, antiphons, and songs, as well as by actions, gestures, and bodily attitudes. And at the proper times all should observe a reverent silence.

34. The rites should be distinguished by a noble simplicity; they should be short, clear, and unencumbered by useless repetitions; they should be within the people's powers of comprehension, and normally should not require much explanation.

36. Particular law remaining in force, the use of the Latin language is to be preserved in the Latin rites.
[...] the use of the mother tongue, whether in the Mass, the administration of the sacraments, or other parts of the liturgy, frequently may be of great advantage to the people, the limits of its employment may be extended.
[...]

54. In Masses which are celebrated with the people, a suitable place may be allotted to their mother tongue. This is to apply in the first place to the readings and "the common prayer," but also, as local conditions may warrant, to those parts which pertain to the people, according to tho norm laid down in Art. 36 of this Constitution.
Nevertheless steps should be taken so that the faithful may also be able to say or to sing together in Latin those parts of the Ordinary of the Mass which pertain to them.
[...]

112. The musical tradition of the universal Church is a treasure of inestimable value, greater even than that of any other art. The main reason for this pre-eminence is that, as sacred song united to the words, it forms a necessary or integral part of the solemn liturgy.
Holy Scripture, indeed, has bestowed praise upon sacred song (42), and the same may be said of the fathers of the Church and of the Roman pontiffs who in recent times, led by St. Pius X, have explained more precisely the ministerial function supplied by sacred music in the service of the Lord.
Therefore sacred music is to be considered the more holy in proportion as it is more closely connected with the liturgical action, whether it adds delight to prayer, fosters unity of minds, or confers greater solemnity upon the sacred rites. But the Church approves of all forms of true art having the needed qualities, and admits them into divine worship.
[...]

114. The treasure of sacred music is to be preserved and fostered with great care. Choirs must be diligently promoted, especially in cathedral churches; [...]

116. The Church acknowledges Gregorian chant as specially suited to the Roman liturgy: therefore, other things being equal, it should be given pride of place in liturgical services.
But other kinds of sacred music, especially polyphony, are by no means excluded from liturgical celebrations, so long as they accord with the spirit of the liturgical action, as laid down in Art. 30.

118. Religious singing by the people is to be intelligently fostered so that in devotions and sacred exercises, as also during liturgical services, the voices of the faithful may ring out according to the norms and requirements of the rubrics.

120. In the Latin Church the pipe organ is to be held in high esteem, for it is the traditional musical instrument which adds a wonderful splendor to the Church's ceremonies and powerfully lifts up man's mind to God and to higher things.
But other instruments also may be admitted for use in divine worship, with the knowledge and consent of the competent territorial authority, [...], however, only on condition that the instruments are suitable, or can be made suitable, for sacred use, accord with the dignity of the temple, and truly contribute to the edification of the faithful.